1. Field of the Invention
The present invention relates to a method of producing a core for magnetic head, and more particularly relates to a method of producing a core for magnetic head having track formed by a laser-induced etching wherein a thermochemical reaction is induced by a laser beam.
2. Related Art Statement
Recently, magnetic recorders, such as floppy disc drive (FDD), rigid magnetic disc drive (RDD), VTR or the like, have been steadily high-densified and, accordingly, the track width of the magnetic head tends to become narrower with a higher accuracy. Nowadays, the track width requires a dimensional accuracy lower than .+-.2 .mu.m for VTR and FDD, or lower than .+-.1 .mu.m for RDD.
In forming such cores for magnetic head, there have heretofore been known a laser machining in air of a track portion, which is disclosed in Japanese Patent Application Laid-open Nos. 29,1118/76, 212,617/82, etc. Further, Japanese Patent Application Nos. 117,726/80, 260,408/86, etc. disclose the formation of the track, by laser machining in air, of a core for magnetic head that is made of a high magnetic permeable alloy, such as Sendust (a ferromagnetic Fe-Si-Al alloy) or the like, or of a composite core for magnetic head that is composed of ferrite and a high magnetic permeable alloy.
However, according to these methods, since the temperature of the material to be machined reaches above the melting point temperature of the material, a processing strain due to heat is formed on the machined surface, accompanied with the formation of cracks on the surface, and properties of the resulting magnetic head are deteriorated. Further, these methods have presented problems such that melted and solidified substances or melted and scattered substances adhere to the machined surface and the vicinity thereof, as well as problems, such as a thermal strain, cracks or the like, to deteriorate the surface roughness or dimensional accuracy, which do not allow a track processing of high accuracy to be conducted with a dimensional accuracy lower than .+-.2 .mu.m, which has recently been strongly required.
Meanwhile, Japanese Patent Application Laid-open No. 60,995/85, the Precision Machine Society, 1985, Spring Symposium, Scientific Lecture Articles (Presentation No. 404) and Engineering Materials, 33, No. 14 (P.57.about.p.62) disclose, in a field other than the magnetic head processing, three methods of machining ceramics, such as ferrite, Si.sub.3 N.sub.4, SiC or the like, by a laser-induced etching wherein a laser beam is irradiated in a potassium hydroxide aqueous solution. However, any of these methods disclosed in the above references lack requirements for obtaining a high accuracy which is necessary for the magnetic head processing, so that the machining with such an accuracy as required in the magnetic head processing has not been performable.